Graphs 1: line graphs

In geography several different types of graph are used to represent all sorts of statistical datastatistical data: information in numerical form, usually presented in tables. The commonest types are line graphs, bar graphs and pie charts.

Most graphs have two axes: the X axis is horizontal (across the bottom) while the Y axis is vertical (up the left side). The two axes each represent a different set of datadata: information without context, eg a list of students with numbers beside their names is data, when it's made clear that those numbers represent their placing in a 100 metre race, the data becomes information. Line graphs are drawn by plotting points (the more points the better) by their X and Y coordinates, then joining them together or drawing a line through the middle.

The graph below is a line graph showing how energy consumption is expected to rise, while consumption of fossil fuelsfossil fuels: Fossil fuels, such as coal, gas and oil, are mined from the earth. They are formed from broken down animals and plants that died a very long time ago. Fossil fuels are burnt to produce energy. Often they are used to create electricity. As they can only be used once, these are called finite fuels. falls and consumption of renewablerenewable: A renewable resource is one that can be replaced or replenished as it is used. Renewable energy is energy which is generated from sources which are not finite or exhaustible such as wave power, wind power, solar power or geothermal energy. energy increases.

Graph showing demand for energy

Types of line graph

Comparison

Sometimes line graphs will represent different sets of data on the same line graph, so comparisons can be made. This is sometimes called a comparison line graph.

Compound

If information can be subdivided into two (or more) types of data - eg total population growth, female population growth and male population growth - then all three can be drawn on the graph. This type of line graph is called a compound line graph.

Scatter

Where the points on a graph do not map into a neat line, a line is drawn through the middle of the points to show the trend or correlation. This is called a scatter graph.